Field of the Invention
The invention relates to a wireless communication device and, more specifically, to a radiofrequency (RF) front-end circuit of a wireless communication device.
Description of the Related Art
With the development of wireless communication technology, wireless communication devices are popular in our daily life. Generally, wireless signals are transmitted or received via an antenna configured at the wireless communication devices. Conventionally, a common wireless communication system includes a mobile communication system (such as GSM, 3G, LTE), a wireless local area network (such as Wi-Fi, WiMax), a wireless personal-area network (such as Bluetooth) or a Global Positioning System (GPS). To prevent mutual interference among the signals from different wireless communication systems, different operating frequency bands and communication technologies (including modulation, coding and encryption) are used by different wireless communication systems. Since the spectrum resources are limited, some of the wireless communication systems need to use similar operating frequency bands. For example, according to the communication protocols IEEE 802.15.1 and IEEE 802.11 for Bluetooth and Wi-Fi, their operating frequency bands are near 2.4 GHz in the industrial, scientific and medical (ISM) frequency band (for IEEE 802.11a, the operating frequency bands are at 5 GHz).
A wireless communication device with multiple wireless communication systems usually has a plurality of antennas. It is preferred that each wireless communication system has its exclusive and independent antenna. However, a space for the antennas is limited in consideration of the size of the wireless communication device and the design requirement. Therefore, to reduce the space for antennas, two wireless communication systems (such as Bluetooth and Wi-Fi) using similar operating frequency bands are configured to share one antenna. However, in this case, when the first wireless communication system communicates via the shared antenna, the second wireless communication system has to stop the communication with the shared antenna. Thus, the communication efficiency of the second wireless communication system is reduced.